They make “creatures” (this set comes with several different kinds of eyes, wings, and feet), houses, roads, and other complex objects that only a 5 year-old could understand.
The pieces are plastic, but seem very durable. The colors are bright and fun. Everything fits together very easily so no help from Mom is required (a definite plus!).
Kid K’nex is designed for younger children. The pieces are larger than the ordinary K’nex sets (labeled age 5 and up). Amazon lists the recommended age for this set as 36 months – 7 years, and I would say that it is probably pretty accurate.
There are other sets available too. We might be adding to our collection on a future birthday!